Dual elevator system and control



F. J. SPRAGUE DUAL ELEVTOR SYSTEM` AND CONTROL June 10, 1930.

Filed nec. 51, 192e 7 sheets-sheet /N VEN TOR.

)gi Vil lune 1o, 1930. y

, F. J. sPRAGuE DUAL ELEVATORSYSTEM AND CONTROL i Filed Dec. 51., 1926 '7 sheets-sheet' '2.

55ay L f1 c5'.

' /NVEN 01a A HORN/ V5.5

^ `lune l0, 1930.

F. J. SPRAGUE DUAL ELEVATOR SYSTEM AND CONTROL 'iFiled Deo. 31, l1926 7 Sheets-Sheet 3 [NVE TOR.

ATTORNEYS.

June l0, 1930. F .1. SPRAGUE 1,763,198

DUAL ELEVATOR SYSTEM AND CONTROL Filed Dec. 51, 1926 v sheets-sheet 4 X VTOR.

BY Y

A TOR/VEN,

June l0, 1 930. F 1, SPRAGUE l 1,763,198

DUAL ELEVATOR SYSTEM AND CONTROL Filed Dec. 31, 1926 '7 Sheetssheet 5 ATTORNEYS.

June 10, 1930. F. .1. SPRAGUE 1,763,198

Y DUAL ELEVATOR SYSTEM AND CONTROL Filed Dec. 5l, 1926 '7 Sheets-Sheet 6A June 10, 1930.

F. J. SPRAGUE 1,763,198

DUAL ELEVATOR SYSTEM AND CONTROLy Filed Deo. 31, 1926 7 Sheets-Sheet 7 Prg/U ATTORNEYS.

Patented` June 1 0, 51930 i UNITED STATES PATENT OFFICE FRANKJ. SPRAGUE, or NEW yoRK, N. Y., AssIGNoR To WEsTINGHoUsE ELECTRIC & MANUFACTURING coMPANSLA CORPORATION or PENNSYLVANIA DUAL ELEVATOR SYSTEM AND CONTROL Application led December 31, 1926. Serial No. 158,244.

My 'invention has for its object an increase in the economical equipment and operation of high buildings, with consequent simplification of ioor lay-outs, by a con- 5 centration of elevators in more limited space than now usually occupied, with resultant increase in available rental space, of an annual value amounting in typical instances of existing buildings to large sums, as will bespeci-ically illustrated later.

In buildings of this character the elevator service 'is divided. In some, local service is provided from a basement or main floor to some floor intermediate between the main and upper ones, stopping at all intermediate floors, and express elevators to the upper limit reached by the local service, or the ioor above, with local service beyond that to the top floor. I

A building with the elevator service thus divided may be regarded as a composite of two buildings, one on top of the other, the lower provided with an elevator service stopping at all floors, and with its shafts not extended into the upper buildings, and the upper sections with an elevator service likewise stopping at a limited number of floors, but with the shafts extending downwards through the lower section. In such buildings it is evident that muchl valuable space is sacrificed throughout all floors except the main floor of the lower unit solely for access to the upper one by elevators having no operative function and serving no i useful purpose in the lower unit except at the ground floor.

In other buildings the elevator service may be divided into three or. four heights of run, each locally serving a fifth or a quarter 40 of the floors. In-such cases, at least the space below the first sto in any elevator, and above the lower landing, is taken away from otherwise useful space, and if an elevator is stopped short of its maximum run then the space above the last vstop is also wasted.

The increasing height and capacity of buildings due to special demands and to the .increased cost of land-all impelled by the demands of competitive investment,-

and certain limitations imposed by law or by the requirements of light and ventilation have steadily increased the cost of elevator equipment and the waste of non-rental space imposed thereby.

To reduce this waste there has been an increase in the running speed of elevators, supplemented by` various devices for automatic stopping and levelling at floors regardless of accurate operation by the operators, but there is a definite limit to the economical speed at which elevators may be operated, and also to the gain which may be made by automatic stopping and floor levelling devices.' v

My invention purposes to reduce the waste of space, by installing and operating on the same rails a pair of elevators in a common shaft, using common or separate counterweight rails for both elevators, any shaft being thus available for elevators runningv from the main floor to supply local service to two different floor zones, with express service to the lower ioor of the upper zone. I also provide means of control such as will permit each elevator to be operated with entire freedom as regards the other except when approaching within a predetermined distance of each other, whether such approach be .the result of one car being'run towards the other at stop, or one overtaking the other when moving in the same direction,

or both in motion'towards each other.

Manifestly, this result can only be accomplished by providing a control for approach movements of the elevators which shall beinterlocked with the movements of regardless of the location ofthe cars relative tothe various landing floors.' o A The control zone, therefore, must be -a floating one, shifting automatically from floor to floor, at one time covering, for example, the firstasecond and third floors, and at another, say, the fifteenth, 4sixteenth and seventeenth floors,r-in fact, any group of three floors, wherever situated, within the prescribed common runs.

In all normal present elevator operation slow-down and stop limits are provided at each end of the run, these being known as the upper and lower limits. Regardless of what other control be added to a dual elevator operation, it is evident that the upper elevator must have the regular up limit and the lower elevator must have the normal low limit. The lower elevator may also, but not necessarily, have a fixed upper limit.

But it is equally clear that each.A elevator must also have a floating limit, a low vone for the upper elevator and an up one for the lower elevator, each of these limits being automatically I variable equally by the movements of each. .That is, the limit o f up travel for the lower elevator and the limit of down travel of the -upper elevator are determined by the shortening of the distance between the elevators to the predetermined zone or distance regardless of floor relation or whether one or both elevators are in motion. I

There is, therefore, provided in my system a fixed up limi't for the upper or express elevator, a fixed low limit for the lower or local elevator, with or without a fixed up limit for the latter, and a floating low limit for the upper elevator and a'iloating up limit for the lower one,-these floating limits being automaticallydetermined by the relative movement and proximity of the elevators themselves, vwhether by movements of the elevator driving mechanisms, the overhead or idler sheaves, or sheaves driven by the car cables, or by running cables attached to and moving with the elevator cars.

Evidently, the motion of the interconnected and co-related governing parts,--eacl1` corresponding to the actual movement of its corresponding elevator, these two governing the differential control of the variable limits,-must coordinate in time, rate and amount of movement of the elevators, unaffected hy any slip of cables on the driving sheaves.

and determined The construction of the electric mechanism, the vsuspension of the cars, and the possible in detail propose and have put in operation in an operative equipment provides a di'erential control of the circuits governing the down movement of the upper elevator and the up movement 'of the lower elevator, this control being made possible by carrying these specific circuits through a float-ing mechanism, like a jack-in-the-box combination,

spider with gears meshing with the motor 1 shaffgear. If the motor car is lifted up either wheel may be turned while the other is held fast, in which case the spider will turn in the same direction as the running wheelat half the angular velocity. If the wheels are turned in opposite directions then the spider will have a differential motion, being anything from Zero to near half speed in either dire'ction, depending upon which wheel turns faster, but if both wheels are turned in the same direction the spider will have a differential speed varying from one-half to full angular velocity, depending upon the rate and relation of the two speeds. f

So in the elevator control mechanism I have invented, the differential member will move fast or slow in one direction or other, or ',stop, depending .upon the direction and rates of movement of the two elevators. But one thing is especially to be noted, and that is, that the two initial drives'are so arranged that up movement of the lower elevator and down movement of the upper elevator will move the differential member of the control mechanism in the same direction, t'o a slow-down and then to a stop position.

vOf course, the elevators are at all times free to move in directions away from each other, no matter how\close they may be, and cars may also move with entire freedom up or down, within normal `extreme limits, when removed from each other by more than the limit of the floating Zone; and each elevatorl may also `move slowly towards the other to stop in the floating control zone. y

In addition to the control of the elevators, various practical physical problems exist for which provision must be made.

The first of these relates to the lower landing stops and the car suspensions. The

preferable plan is to have the express elevator start from the main floor and begin its local stops at the nth .or nth-plus-one floor, and to have the local elevator start from the basement or sub-basement, with stops at all oors, including the main, to, say, the nth fioor, its upper run being ordinarily limited to su'ch floors as will best meet the joint operation. Of course, each elevator may have its control interlocked with the landing doois on the floors which it serves, and such control may be eliminated or be specially. arranged at the first or main floor.

The cars mayand preferably shouldbe run on the saine rails, and thecounterweights may be run on the same or different counterweight rails. If on the same rails the counterweight for the express. elevator would be the lower. The suspensions may be varied, the express having center cable fastenings and the local side fastenings, although both may have side fastenin s.

lhe usual car safeties may be used, such as the normally locked mechanisms released at an excess speed, whether because "of loss of control or broken cables or fastenings, through a running rope fastened to the car with a locking centrifugal at the head of the shaft. Or, and preferably, a combination of initiating of safety means,one depending upon speed and the other local to the ear and dependent upon rate of acceleration, which will form the substance of another patent application.

In laying out the floor plans of some types of buildings, the halving of the number of elevator shafts makes for simplicity, as all shafts may be run .through the full height, landings may be provided at all floors, the floor plans as regards windows and spaces available for offices may be made identical, and the elevator service be made far more flexible to accommodate changesl in occupancy or seasonable or hourly change in requirements.

The drawings and description of particular'mechanisnis are simply typical, and

are not intended as a limitation upon the application of the general principle of construction and operation of my method of dual control of elevators in a common shaft.

Referring to the accompanying drawings, in which corresponding parts are designated by like marks of reference.

Fig. 1 shows a plan view of two elevator operating motors, the driving shafts thereof, traction sheaves driven thereby, and three limit switches, namely, the up limit circuit controller for the upper elevator, the low limit circuit controller for the lower elevator, and the common differential controller for the shiftable variable of both elevators.

Fig. 2 shows an elevation of the two motors and of the center or express traction sheaves, the corresponding idler sheaves, and the electric brakes on the two motor shafts.

Fig. 2a shows the roping orcabliiig scheme for support of the two elevators, the upper elevator being supported by center positioned and anchored cables and the lower elevator by. side positioned and anchored cables, the reversed arrangement of the counterweights when run on common rails and the method of leading the cables to the counterweights.

Fig.' 3 shows a side elevation of the lower or local elevator niotor, its driving shaft, the traction sheaves and driving gears for both the upper and lower elevators, the idlers below the traction sheaves, the electric brakes on the driving shaft of the lower elevator motor, and the worm gear drive of one end ofthe differential limit controller.

Fig. 3a shows a typical physical construction .of the differential gear drive for the variable limit controller for the up control circuit of the lower elevator and the down control circuit -of the upper elevator, regardless of the particular physical means 'of driving each primary pait.

Fig. il is schematic diagram of the operating electric circuits and their relation to the limit switches, developed in plan, when the express or upper elevator is moving down and the local or lower elevator is moving up, that is, when approaching each other, and at full speed.

Fig. 5 is a schematic diagram of the oper` ating circuits and their relation to the limit switches, developed iii plan, when both the express and local elevators are moving down at full speed.

Fig. G is a schematic diagram of the operating eircuits and their relation to the limit switches, developed in plan, when the express elevator is moving/up and the local elevator is moving down,'that is, away from each other, and at full speed.

Fig. 7 is a schematic diagram of the operating circuits and their relation to the limit switches, Ideveloped in plan, when the cxpress and local elevators are both moving up, also at full speed.' A

Figs. '8 to let are diagrammatic illustrations of the variable relation of two elevators operated in a common shaft at fixedminimum approach distances.

Referring to Figs. l, 2 and 3, which show plan, end and side views of two traction drive elevator motors at the top of a shaft and, for convenience, a method of gear drive ofthe traction sheaves, A is the driving motor for the express elevator and B the driving motor for the local elevator.

The shaft of motor A is connected through a coupling to shaft C, which carfil ioo

beneath it, and is extended through supporting bearings to carry a brake wheel S and a pinion E, meshing into drive gear G.

Secured to this drive gear, on eachl side, is a pair of friction drive traction sheaves K, K, over which the cables carrying the express car and counterweight are carried with what is known as a double wrap, the cables J from the car-being rst carried over onejpair of sheaves, then around idler sheaves l supported below the traction drive sheaves and shown in detail in Figs 2 and 3, and then again over the remaining pair of traction drive sheaves K, and 'on down to the counterweight.

Similarly, the shaft of motor B, that which operates the local or lower elevator, is coupled to a shaft D, which is extended, through suitable bearings, to carry a worm Y'meshing with a worm a brake wheel S, and a pinion F which enages the driving to the shaft M.

Fastened to the -driving gear H. is a pair of friction traction drive sheaves `which carry one-half` of the supporting cables of the local elevator, while to the shaft M is secured another pair of traction sheaves for the other halfof the cables of the local car.

Shaft M is carried by and turns in bearings at each end, and upon the same shaft and freely journalled upon it, for convenienee, is carried the .driving gear and sheaves for the express elevator.

The cables for the local car are rove in the same fashion as those for the express car, with double wrap, the loop being carried around individual idler sheaves mounted bellow the friction drive sheaves. The object of this double wrap is to increase the friction grip', and to reduce the chance of slip at starting and stopping. l

The system thus shown is one which, with certain proportions and dispositions of loads and weights of cars and` counterweights is in a balanced condition, and will thus operate with -a minimum expenditure `of power. In regular operation, however, the balance of load shifts, sometimes being in excess on the car side and at other times on the counterweight side, and, hence, with ,a suitable motor currentw-ill sometimes be taken from, and at other times be delivered to the supply source.

Fig. 2a, which is inserted for illustrative purposes only, since the subject matter thereof forms no part of my invention, shows the actual relation of` the two cars Xp and Lpand theirrespective counterweights Cx and CZ` when the two latter are run on the same rails, one above the other. In this diagram the driving motor and gears are omitted, as .well as certain other features, such as the idlers, shown in Figs.

gear beneath it,

gear H, rigidly connected or upper car Xp are secured to the center of the lower counterweight Cgthese cables passing through an opening in the center of the upper counterweight GZ.

normally pressed, when the operating circuit is broken, by a friction shoe u, held against the bra wheel by adjustable spring c. When in operation, magnet V V being energized, the brake shoe is retracted and leaves the brake wheel and shaft unretarded. i

The all important element of this combination of a pair of elevator mechanisms driving a pair of elevators in a common shaft is the provision for interlocking the movement of the cablesv and cars so that a normal minimum approach distance may be insured between the cars at all times, regardless of their lrelative location in the shaft. 'lhisis secured by a differential combination which controls a shiftable up limit for the lower or local car and a shiftable low limit' for the upper or express car.

Fig. 3a shows a typical form illustrative of the differential mechanism which may be used in the supplemental limit controller.

vThis comprises a control member, rotatable -about a horizontal axle, and carrying on its `gears on the spider, which side gears rotate about the same axis as the latter.` If one of the side gears is held fast, rotation of the other will rotate the spider in the same direction at half speed, its free gear being driven around the stationary one as a runway. Y

If both gears are turned in the same direction, the spider will turn more rapidly, and if`both move at the same rate then the spider will turn at a like rate.

If, on the other hand, the side gears turn in opposite directions, the spider will either remain stationary, as when the speed of the side gears are alike, or take a' differential motion of variable rate, one way ory the other, according to the relative movements and speeds of the side gears.

e It follows that if one of the side gears is driven by or in synchronism with one elevator and the other side gear is driven by or lin synchronism with the other elevator, and the central member is made to control cer` On each driver shaft is a brake wheel S,

lao

tain circuits, these circuits may be opened or closed according to the direction and amount of displacement of .the contact spider as -a .differentiated result of the motion of two side drives.

In the figures gear Q1 is shown, for' illustration, driven by a worm gear and the gear Q2 by a spur gear, but it is evident that anyl vkind'of a driving connection to the motor or motor loads may be used, and also that a variety of well-known circuit controlling contacts and opening and closing devices may be operated by the differential member without ldeparting'from the spirit of my invention.

As already stated, it is essential, toavoid the necessity of adjustment, that the prime motivating agencies operating this differential control shall be free from tendency to change the limit of approach distance between the two elevators in the event of any slip of cables on the driving sheaves, and hence it would best be operated from either the idler sheaves, which are largely free from slip, or friction sheaves driven by the cables, or by running ropes attached to and moving with the car. But where the duty is not too severe the differential may be driven from the elevator motors themselves, and for convenience of illustration this method is` shown in Figs. l-B.

In the middlespace between the driving shafts is carried a jack-in-the-box, that is., a spider P, rotatable about a horizontal axis and' having on its extended arms freely turning mitre or bevel gears Q, which are engaged on each side b v suitable mitre or. bevel gears Q-l and Q-2- The first of thesevis carried on shaft Z, which also carries a worm wheel X1, meshing with worm X, and hence is turned at a proportionate rate bythe shaft of the express elevator motor A, While the latter is carried on shaft Z1, whichvalso carries a worm wheel Y1, meshing with worm Y, and hence is moved at a proportionate rate by the shaft of the local elevator' motor B. On the outer end of one shaft is carried the fixed up limit contact cylinder U of the express elevator, and on the outer end of the other shaft is carried the fixed low limit contact cylinder T 'of the local elevator. The worm gear of one drive is right-handed and of the other left-handed, so that when theexpress elevator is moving down or the local elevator is moving up, the differential member is turned ,in the same direction, that 1s, to the contact breakingposition. If both are moving in the opposite directions, that 1s, the express up and-the local down, the differential is turned in the reverse direction, that is away from the contact breaking posi-` tion.

Any change in direction, rate, or amount of movement of either 'or both of the driving members of the differential is reflected in varying fashion in the middle, or differential member, so that it will move one way or the other, fast or slow, and with any angular displacement up to the maximum, which must, of' course, be less than a complete circle, in response to the variable motions of the elevators.

Resting on the fixed up limit contactcylinder U of the express elevator are brushes yl, 2, 3 and on the fixed low limit contact cylinder T of the local elevator are brushes 10, 11, 12, which provide a line contact supply and slow-down and stop limits, as shown and explained in Figs. 4-7.

Also, resting on the contact differential are six brushes 4, 5, 6, 7, 8 and 9, which, as also shown in Figs. 4 7, provide the necessary circuits for the shiftable down limit of the express elevator and the shiftable up limit of the local elevator, the` contact cylinders being cut away in such fashion as to insure first a slowdown and then a stop, as shown in the figures referred to.

The distance between the elevators, which must not be encroached upon inpnormal operation, is determined by the meshing of the gears, in connection with the set of the fixed limits, 'and by the relation of the broken or stepped end of the contact cylinder' R, to the contacts resting upon it. Hence, if the meshing has been determined for any given set of the fixed limits, then the approach distance may be changed by rotat-A ing the contact cylinder R about its supportin differential member.

igs. 4-7 are diagrams of. the dispositions of one type of control circuit in operating condition for effecting the control of two elevators in my dual system, with particular -rference to the method of differential control of the shiftable u per limit of the lower elevator and the sliftable lower limit of the upper elevator, provision being, of course, made for the `fixed up limit of the upper elevator and fixed low limit of the lower elevator, a fixed up limit for the latter, although it may be used, being omitted as unnecessary. l

Fa and Fb are the field circuits of Aa and Bb, the armatures of the express and local or upper and lower elevators, respectively, all supplied from a common source To each armature are connected, respectively, the contact arms o, o, in movable engagement withthe resistances a, b, c, d, and p, p in movable engagement with resistances e h. f

, ittgthe top of each figure is shown the upper limit cylinder control switch U for the express elevator, and the down limit con-` trol switch T for the local elevator, whilek in the center is shown the differential controll Cylinder R of the Shiftabie Heating im lima of the express elevator 4and the, shiftable floating up limit of the local elevator,allr Ycontact cylinders being developed in plan.

As shown in Figs. l-3, each elevator mechanism moves its fixed limit switchU or T in the proper direction for cut-off through the worm gear driven shafts.

Through the same means -are independently driven the two bevel or mitre gears Q-l and Q-Q, meshing with the gears Q carried on a freely movable spider P Which supports the differential control contact cylinder R, with which engages the siX brush contacts 4.-, 5, 6, 7, 8 and in the same direction, that is, as developed,...

toward the top of the diagram, when the eX- -press elevator is moving down or the local elevator is moving up, with the result that in a certain predetermined relative position of the elevators both sets of these contacts, controlling the respective limits of motion,

are always broken, first at contacts 4 and 9 through resistanees c and Z, to slow down the elevators, and then at contacts 5 and 8 to stop them.

The differential control cylinder R will move in one way or other, for variable distances, at angular speeds varying from the minimum to the maximum, or will stand still,vaccording tolthe direction and rate of movement of the two driving gears Q-l and Q-2, these being, as already stated, each independently driven by some part of its associated elevator equipment having a motion synchronous with the motion of the corresponding elevator car or car load. Such parts are, for example, the motor shafts, the traction sheaves, or any sheaves or shaft driven by the hoisting cables, as for example the idler sheaves, or by cable fastened to the car and moving with it, as used to operate the ordinary speed control governor.

The sole function of any of these drives is, through a proper ratio of gear reduction, to impart motion to the gears Q1 and Q2 synchronous with the motion of the cars, and thence variably to the diiferentialmember. As shown in Fig. l, the gears Q1 and Q2 .are driven respectively through reduction worm gears Xl `and Y1 and worms X and Y, by the shafts C and D of motors A and B, but it is evident that inasmuch as there would be no change in the ldifferential action itself the gears may derive like motionby being driven from any shaft moved by or in synchronism with the movements of the cars.

These are all physical variants or e uivalents, and admit of a great variety o construction. They also may find their equivalentl in differential screws and nuts or other mechanical forms without departing from the spirit of the invention.

Referring to the figures in detail: Y

In Fig. 4; the control switches of the two cars are set for full down speed of the ex press and full up speed of the local elevator, and the paths of the circuits are as indicated by the arrows and enumerated numbers.

As already explained, the fixedand variable limit switches are shown at the top -of the gure 'and in plan view. 0n the left is the upper limit switch contact cylinder U of the express'elevator, from which a circuit-breaking section iscut away, and on which rests the main contacts l and 3, and

contact 2 in circuit with a slow-down resistance z' when the contact first rests upon the insulating'section of the cylinder. W'hen the express elevator is moving down contact cylinder U is, by means of worm X in mesh with wormwwheel X1, rotated in the direction shown by the arrow, that is, away from the circuitebreaking position.

Similarly, on the right han-'d is shown the low limit switch of the local or lower elevator, with its main circuit contacts 10 and l2, and contact 1l in circuit with a slow-down resistance jwhen the contact first rests on the insulating section. -`When the local elevator is moving up the' contact cylinder T is, through worm wheel Y1 and worm Y, rotated in the direction shown by the arrow, that is, away from the circuit-breaking poJ sition. 1

If the directions of motion of the two elevators are reversed, as indicated in Fig. 7, l

express elevator and `the main 'and slowdown resistance contacts 9, '8 and 7 associated with the up control circuit of the local elevator.

This contact or control c lindei` is carried on the middle member o the differential -ciated with the down control circuit of the controller, that is, the spider section with its freely mounted bevel or mitre gears at the outer ends of its arms, which mesh with the bevel or mitre gears Q1 and` Q, independently driven through their respective worm wheels and worms.

The motion of this cylinder is variable both in direction and rate. If the elevators are running in the same direction at like speeds the cylinder will remain stationary; if the speeds or directions. of motion are differentjthe cylinder will move one way or the other, fast or slow, according to the relative direction and speed of movement of the elevators; if they are approaching each other the cylinder will move at a faster rate, all contacts will be brought into engagement with the insulating section and both elcvators will first be slowed down and then stopped.

This slowing down and stopping will result with either elevator if it only is moving to an approach limit, and at vthe same time the limit will be established for the elevator,

which has been stopped by the regular car controlso that it also can not Abe moved towards the other car.

Inasmuch as this differential control affects only the circuitin each motor which governs the approach of the elevators towards each other, it follows that the motors may be freely operated through the remain-A ing control circuits ina direction away from the approach, until stopped by their normal limits.

In the middle 'part of the diagram thereare shown the starting resistances a, b, c and d of the car controller O O for the express elevator armature Aa, and the starting re' sistances e, f, g, h for the careontroller TT of the local elevator armature Bb; also the circuits Fa and Fb of the two motor fields, and the auxiliary or supplemental control switch Sw, by which either elevator may be moved a short distance toward'nearer approach after being stopped automatically.`

Referring now to the detail circuits, in

the ex ress elevator the armature current A fiows rom the plus source over circuits 31,

32 and 33 to contact 6 on the differential control cylinder R,- thence .across the surface of the latter to contact 4, shunting ythe slow-down resistance k, and thence over circuits 34 and 35 and arm O tov armature Aa, throu'ghfit, over circuit 36, through the electric brake coils V, and by circuit 37 back to the source, no part of the circuit passing4 through'the upper express limit switchy U.

The current of the armatureV of the local elevator likewise fiows from the plus source over circuits A31, 32 and 33 to contactV 6 of the differential control `cylinder R, thence .across it to contact 9, shunting resi-stance l, and then through circuits 38 and 39 and arm p. to armature Bb, and through it via circuit 40, brake magnet coils V1, and circuits 4l and 37 `to the source, no part goin through the low limit switch T.

In consequence, the differential cylinder moves at full angular velocity in the direction shown by the feathered arrow, and

ping of the moving elevator at the predetermined distance.

In Fig. the motion of the local elevator is reversed, so that the current of its armature Bb, instead of passing through the differential control cylinder R as in Fig. 4, passes from the plus source over circuits 3l and 42, armature Bb, circuit l43 to contact .12 of the upper limit cylinder switch 1T,

across the surface of the switch to contact 10, normally shunting the slow-down resistance j, and then by circuit 44, brake coil V1 and circuits 4l and 37 back to the w source` As a result, the differential control `cylinder R will remain stationary if the speeds of the rcars are equal, or will have a variable movement in one direction or the other at less than half angular velocity, de-

i pending upon the relative speeds and directions of movement ofthe elevators.

Should either elevator be at stop thedifferential control cylinder will stop the` movement of the other elevator atpthe predetermined distance, as well as open its own approach circuit.

In- Fig. 6 the circuits are set so that the I express velevator is moving up and the local elevator down, and the active circuits of neither pass through the differential control cylinder R but each passes through the respective fixed limit switches U and T.

l l i) Here the circuit of the local elevator I motor remains the same as shown and described inv Fig. 5, but .the current'of the exn press elevator motor flows from the plus source via circuits 31, 32 and 45, armature Aa in a reversed direction to that shown in Figs. 3 and 4, circuit 46 to contact 1 on the upper limit control cylinder switch U, thence across its surface to contact 3, and through circuit 47, brake coil V and circuit 37 to the .minus source. As a result, the differential control c linder R will move at a Velocity varying irom half to :full rate away from the contact breaking position, and neither shiftable limit will be operated, although each car will be under final control of its fixed limit.

In Fig. 7 the circuits are such that the exor express elevator passesthrough its upper limit U, and not at all through the contacts of the differential cylinder R, the up circuit of the local elevator does pass throu h the differenti-al cylinder contacts'. Here t e circuit of the expresselevator motor remains the same asfshownand described in Fig. 6, while thcir'cuit of the local elevator motor i-s the same as shown and described in Fig. 4,-that is, from plus source via. circuits 31, 32 and 33, contacts 6 and 9, circuits 38, 3 9, armature Bb, circuit Ll0, brake coil V1, circuitswl and B7 to negative source. So long as-thespee'd of the'levatorsis the same dilerential cylinder will remain stationary,lbut if thc local elevator overhauls the express, whether because the latter is stopped or because it-is moving more slowly, then when the predetermined distance between the elevators is reached the local elei vator will stop.

We have, therefore, a differential cont-rol member whose angular velocity, and limit .and directionof movement, is the resultant of two variably speeded reversible driving members, each individual to its own elevator, with means jointly operated by them to modiyand interrupt the down circuit iof the upper elevator and the u circuit ot the lower one,'tov insure slowing down and stopping each elevator when the limit of the approach distance between them is reached` The position of vthe differential control cylinder R with reference to the two driving members determines the limiting approach operating distance Vof th`e two elevators. Hence, by turning the shell R one way or other about its supporting Heating gear frame the limiting distance'may be changed at will without changing the fixed upperl limit of the express elevator` or the xed lower limit of the local elevator.

A supplemental control is effected by switch Sw, which may complete the circuit of the armature of either elevator motor, through resistance m or n, so that they can be brought slowly together more closely than may be perhaps permitted by the normal car control, this secondary or -additional control being manipulated eitherwithin a car by the operator or without by the starter.

The circuits indicated vand the actual' method of controlling them tors by resistances directly varied by cont ols in each car is operative, but it is to be understood that any of the usu'al methods of distant control,

as evidenced, among others, in Sprague multiple-unit Patent No. 660,065, as well asin other published patents and incurrent practice, may be used, such as the master'control of unit resistances located at or near the elevator machinery, or resistances controlled 'by a solenoid or pilotl motor, or by a variable potential I control from a generator Whose field strength is varied; and, of

course, any combination of these with autocally making small movements for floor levelling purposes.

ing, withthe express elevator Xp startingV from the main floor, and the local elevator Lp starting from the basement or sub-basement, operating in different locations and directions over a cycle of a complete up and down trip for each "elevator,

In Fig. 8 the express elevator is shown| at thel main floorlready for loading and the local elevator in the basement waiting for the express elevator to move out of the Way.

In Fig. 9 the express elevator has gone to its first stop at, say, the 18th Hoor, and the local elevator has run up from the basement to the main fioor where it has loaded and and is ready to start.

In Fig. 10 the express elevator has gone on making its local stops until it has reached its upper limit at the 30th Hoon-and, mean.- while, the'local elevator has gone onmaking whatever stops are necessary vand has arrived at the 18th floor, an arbitrary limit of its service, but one which may be changed at will. f l' ing downtrips, with local Astopsin their refV spective zones, the expressffor: example, be.- ing at the 27th ioor andbthe "local at the 15th.

In Fig. 12 the local has stoppedat` the 12th, and the express has overhauled it at the lth'and has been stopped at the predetermined zone distance of three iioors.

' In Fig. 18 the llocal elevator has resumed its way and is passing, or has stopped at, the 8th ioor, while 'the express elevator h followed the local at ,the ioating distance Jznd is abreast of, or has stopped at, the 11th oor.

In Figf'lll the elevators are shown the same distance apart, the local having made its lower limit'inl the basement and the ex- Iress having reached the 3rd ioor on the way own.

matic stoppingof elevators or for automativloo 'Ihe` automatic slowing down and stopping has thus far been under normal control, but, as has been explained with reference to Figs. 4-7, the two elevators ma now, through an extra control provision, be

brought closer together, either from Within the cars, or from outside by the starter, and

the position ofi-starting shown in Fig. 8 be movement of the driving gears.

manually operated controllers for each of the motors anda sup lemental automatically operatedcontroller or one only of the two direction controllinfr circuits of each of the motors, said controler comprising a reversible floating member Vcontrolling said circuits by means of a revolvable spider having gears mounted so as to freely rotate about its radial axes, and gears on each side of and engaging the spider' gears independently driven by the two motors.

2. .In a control system for two independent reversible motors, the combination of manually operated controllers for each of the motors and a supplemental automatically operated controller for one only of the two direction circuits of each of the motors, said controller comprising a revolvable and reversible central member controlling said circuits, and driving gears in engagement with independently and reversibly driven gears on each side thereof, the central member having a differential motion in either direction varyin in rate from nothing to a maximum, accor ing to the ratel and direction of 3. In a controlling system for two independent reversible motors, the combination -of manually operated controllers for each of the two motors, and a supplemental automatically operated controller for one only of the two direction circuits of each of the' motors, said controller comprising three members having a common axial center of rotation, the two outer members being. niitre or bevel gears independently driven by the two motors at variable speeds in either direction and in imesh with freely turning gears on a lspider carrying an intermediate circuit controlli member, thisvlatter membei'` having a di erential motion in 'either direction .variable in rate and displacement according to the direction-and' rate of motion of the two drivinggears.

4. In a controlling systemy for two independent reversible motors, the combination of manuallyr operated controllers for eachof the motors and a supplemental automatically operated controller for one only of the two direction circuits 'of each of the motors, said. controller comprising "af diferential member having a reversible movement varying in limit, direction and rate according to the amount, direction and rate of movement of each of two independently driven members in connection'therewith'.

5.V In'a dual elevator system, the conibinat tion'of ytwo'ele'vators operating `in a com-I mon shaft, each elevator having iniaddition to an extreme limit of travel in one direction afloating limit oftravel in the opposite direction, theloating limits of the two elevators fbeing simultaneously determined for both ofthe elevators by a sup lemental controller situated at the head ofp the xshaft and differentially two elevators.

6. In a dual elevator system comprising two elevators operati-ng in a common-shaft,

operated by movement of the means operated by each elevator for caus-l rupting the operation of the first-mentioned means whenever the elevators approach each other within a predetermined distance, said means comprising a supplemental controller situated at the head of the shaft and differentially operated to control the approach circuits only by 'movement ofk the two elevatois.

8. In a dualelevator system comprising two elevators operating in a common shaft, one above\thc other, the combination of means for governing the up movement of the lower elevator and the down movementr of. the lupper elevator, and means for inter-` rupting the operation-of the first-mentioned means whenever the elevators approach each other within a predetermined distance, said latter means comprising a supplemental controller situated at the head of the shaft and differentially operated to control the approach circuits only Aby movement of the two elevators, and means for changing the predetermined distance.

,9. In a/dual elevatorsystem comprising.

two el'evatorsopeiating in a common'shaft, the combination of individual controllers for each elevator and a floating or differential control liiiiit controller for each elevator vtwo elevators operating in a common shaft, va floating or differential control limit for each elevator controlled by the movement of a mechanism synchronous with the movement of one of the elevators when the other is stopped.` y

n l1. lIn, a dual elevator system comprising two elevators operating in a common shaft,

a floating or differential control limit for each elevator operated jointlyby the movementof mechanism operating synchronously with the movement of either elevator when one elevator is overhauling the other.

12. In a dual elevator systemV comprising two elevators operating in a common shaft,

a oating or diiiereiitial control limit for each elevator operated jointly by a mechanism whose primary movements are synchronous with the motion of each elevator, to establish approach limits regardless of location of said approach in relation to the different floor levels.

13. In a dual elevator system comprising two elevators operating in a common shaft,l

a floatingv or differential control limit operated by mechanisms whose primary vmovements are synchronous with the movement' elevators.

-15. In adualelevator system the combina-J.

tion otwo cars operating on common rails in a single shaft anda supplemental controller at the head of the shaft for the down control circuit of the upper car andthe up control circuit of the lower car., carried through a diierentially opcratedniember operated by two gears cachot which is driven by its associated motor.

16. In a dual elevator system comprising two cars operating on common rails in- .a

Cil

single shaft, the combination of controlling circuits for the movement of both cars so connected as to insure the slowing downl and stopping of either or both cars when brought within a predetermined distance of each. other through the medium of a' differential :circuit controllerreversibly driven by independent mechanisms movingin synclironism4 with the two elevators, and a supplemental manually operated control 'permitting the two cars to be broiight nearerto each other.

17. Ina system of control for two inde'- pendent reversible motors', the Combination of a manual controller for each of the motors and a supplemental controller comlirisiiig a floating member controlling one .eac-h of two direction controlling circuits or: the twomotors, said member being movable in variable ainount, rate and direction by two con# nectedgears each of which is driven in synclironisiii .with one of ,the motors 4and .its motor load. i

18'. In a4 dual system of elevator control, the combination of' two independent'revers-l ible motors situated at the head offa. shaft each connected to an elevator car, a manually operated controller for each motor in its respective car, and an automatically operated supplemental controller for controlling one only ot the two direction circuits ot' each motor, said controller comprising a diil'erential member in constant engagement with and driven. by two connected members each operated in synclironisni with a motor load.

19. In a system of motor control for a dual system of elevators, the combination ot independent manually operated lcontrollers for each elevator motor and a supplemental limiting and automatically operated controllerat the head ofthe shaft for the down circuit of the upper elevator and the up circuit ot' the lower elevator, said controller being operated to a position of simultaneous control of both circuits when the cars are brought within a definite distance of each other, regardless of the method or direction of approach.

20. In a system of control for two elevator motors located at the head of a shaft and operating two cars one above the other in the same sha'ft, a differential limiting controller comprising means opoiatcd'by the upmovement of thelower elevator and the down movement of the. upper elevator to simultaneously open the circuits corresponding to said movements while leaving undisturbed the circuits controlling the opposite movements.

2l. In a'system of dual motor control, the combination ot' two reversibly driven motors, each connected to an independent load, an

independent car controller for both speed and direction for each motorand a common limit-ing controller comprising two parts each reversibly and independently driven in synchronism with a motor load, and another part differentially driven by the aforesaid parts and including one only of the two directing controlling circuits oit' each of the two motors.

22. In a system of motor control, the coinbination of tivo reversibly driven motors, each connected to an independent load,and

lllO

a common limiting controller comprising.

two parts one of which is reversibly and iiidependently driven iii synchronism -with one motor load, and the other' similarly driven in-synchronism with the other motor load, and another part diifercntially driven by the aforesaid controller parts and including one only of the two direction controlling circuits of each of the two motors.

23. In a dual elevator system, the combilnation of two elevators operated one above the other on common' railsI in a lsingle shaft, the upper elevator having center limiting cable suspension and tlielower one a. divided ,side cable suspension, and tree counterweights for eachelevator moved on common rails at the san'ie ,speed as the elevators, the upper counterweight being attached to the side cables of the lower elevator and the 4with those of the manual controllers and is automatically operated in synchronism with the movementof either elevators to simultaneously modify and interrupt the aproach circuits of each elevator without afecting the circuits controlling the movements of Athe elevators away from each other.

25. In a multiple' elevator control system, a plurality ofelevators independently operable in a common shaft, separate driving means moving for each elevator up and down in said shaft, and means located adjacent said driving' means and operable differentiall y in correspondence with move-,

ments of oth of said elevators for stopping said elevators when they approach within a predetermined distance of each other while permitting freedom of movement of either elevator in. either direction when said elevators are more than said distance apart.

26. In a multiple elevator control system, a plurality of elevator cars independently operable in a common shaft, separate multi-speed drivin means for movin each of said cars up an down inv said sha and means operab differentially in correspondence with the combined movements of said cars for reducing the speed of any of'said cars when said cars approach wlthin one predetermined distance of another, and vfor stopping any of, said cars when said cars approach withinv a lesser distance of each other.

27. In a multiple elevator control system,-

. a plurality of elevator cars independentl operable in a common shaft, separate multlspeed driving means for moving each of said cars up and down in said shaft, and means operable differentially in corres ondence with the combined movements o said cars- -for reducing the speed of any of said cars when said cars approach within one predetermined distance of another, and for stoppingl any of said carsl when said cars approac within a lesser distance of each other, and manually operable means for permitting said vcars to approach each other within said last named dlstance but only at low speed, and means actuated by said differentially operated means for limiting the distance of approach under the control of said manually operable means.

In testimony whereof I have hereunto signed my name, New York,December 30,

FRANK J. S PRAGUE,` 

